The goals of this study are to: 1) document alterations in regional blood flows in the kidney, liver and heart in response to I.V. anesthetic agents; 2) do so in a conscious, chronically-instrumented animal model so as to obtain continuous changes in a preparation not altered by recent surgery and/or simultaneous presence of other anesthetic agents; 3) perform such studies under normal and certain high risk situations (i.e., hypovolemia, heart failure) seen clinically and 4) in this same model, compare these responses to those seen with inhalation anesthesia. After documentation of these changes in renal, hepatic and cardiac hemodynamics in these situations, the intent is then to attempt to work out the mechanism of those alterations which are felt to be significant. This will be accomplished by use of surgical de-afferentiation procedures and autonomic blocking agents to localize the mechanism to either a directly or an indirectly-mediated effect. The hypothesis to be tested is that although intravenous anesthetic agents appear to cause less hemodynamic alteration than inhalation agents, their effects on individual regional circulatory beds may not be as benign as it would appear when only systemic changes are examined.